1. Field of the Invention
The present invention relates to a power transmission device of a vehicle, and more particularly, to a pulley assembly and a method of manufacturing the pulley assembly which transmits driving power to a compressor used in an air conditioner for a vehicle.
2. Background Art
In General, a compressor used in an air conditioner receives refrigerant from an evaporator, converts the refrigerant into a refrigerant gas of high-temperature and high-pressure, and provides it to a condenser.
The compressor used in the air conditioner for a vehicle receives a driving force from an engine through a pulley assembly and compresses refrigerant.
Conventionally, the compressor for the vehicle selectively controls that the driving force of the engine is transmitted to the compressor using an electronic clutch.
However, a variable capacity type compressor does not need the electronic clutch because it selectively carries out a compression operation by regulating an inclination angle of a swash plate according to demands of cooling, and hence, a power transmission device for transmitting the driving force of the engine using the variable capacity type compressor is constructed of a clutchless type.
As shown in FIG. 1, the power transmission device of the clutchless type compressor includes a pulley assembly 10 and a limit assembly 30.
Here, the pulley assembly 10 includes a cylindrical hollow pulley 11 and a bearing 12 mounted on an inner circumferential surface of the pulley 11, and is rotated by receiving a driving force of an engine.
An outer wheel 12a of the bearing 12 is forcedly fixed onto the inner circumferential surface of the pulley 11, and a front housing 1a of the compressor is joined to the inner circumferential surface of an inner wheel 12b of the bearing 12.
Moreover, the limit assembly 30 in lieu of the electronic clutch transmits or blocks out the driving force of the pulley assembly 10 to a driving shaft of the compressor, and is mounted on the surface of an outer wall of the pulley 11 of the pulley assembly 10.
Particularly, the limit assembly 30 rotates the driving shaft 1b while rotating together with the pulley assembly 10, and serves to relieve transmission of the driving force if there is a torque exceeding a predetermined value in the compressor or the driving shaft 1b of the compressor cannot be rotated.
The limit assembly 30 includes a hub 31 joined with the driving shaft 1b, a limit 32 joined with the hub 31, and a limit housing 33 having the limit 32 therein and being joined to the pulley.
The limit 32 is broken to prevent that a rotary force transmitted from the pulley 11 is transmitted to the hub 31 when there is a torque exceeding a predetermined value in the compressor or the driving shaft 1b of the compressor cannot be rotated.
In the meantime, the pulley 11 of the pulley assembly is generally made of a steel material, and hence, there is a limit to reduce the total weight of the pulley assembly.